Automatic stoker



(No Model.) 4 Sheets-Sheet l.

N. W. PRATT. AUTOMATIC STOKE-R.

No. 443,110. Patented Deo. 23, 1890.

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ATOR/WIK (N-o Model.) L 4 Sheets--Sheet 2.

N. W. PRATT.

AUTOMATIC STOKBR.

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ATTORNEY (No Model.) A 4 sheets-sheet s,

N.. W. PRATT. AUTOMATIC STOKBR.

No. 443,.110. 'Patented Deo. 2.3-, 1890. Z1-@f4 Q/ A TTORNEY.

I (N0 MOdGL) l 4 Sheets-Sheet 4.

N. W. PRATT. .AUTOMATIC STOKER.

Patented Deo. 23, 1890.

ATTORNEY.

UNITED STATES PATENT OFFICE.

NAT. V. PRATT, OF BROOKLYN, NEV YORK.

AUTOMATIC sToKER.

SPECIFICATION forming part of Letters Patent No. 443,11, dated December23, 1890. Application filed December 23,1889. Serial No. 334.727. (Nomodel.)

V.To @ZZ whom t may concern:

Be it known that I, NAT. YV. PRATT, a citizen of the United States,residing at Brooklyn,in the countyof Kings and State of New York, haveinvented certain new and useful Improvements in Automatic Stokers, ofwhich the following is a specication.

My invention relates to chain-grate stokers; and it has for its objectto adapt the furnace wherein such a stoker is used to exclude the accessof cold air through the interstices that are usuallyleft between themoving sections of the grate and the furnace-walls or other parts of thefurnace or ash-pit; also to adapt the construction of the furnace toobtaining a maximum efficiency of heat; also to promote convenientaccess to the furnace where it is required to pull the fire or toobserve or regulate the same independent of the feeder; also to separatethe residue of the fuel that has traveled the entire length of thefurnace from the portions of fuel that may fall through the grate atintermediate points and be but partly consumed; also to crush anddistribute the coal evenly upon the grate and apportion asuflicientamount of the body of coal toward the sides of the furnace to form aseal against the direct access of air above the grate; also to promotewater circulation in the boiler and to protect the walls of the furnaceby the introduction of water-pipes that lie proximate to the sides ofthe hre; and in order to enable others skilled in the art to which myinvention appertains to understand and use the same, I will proceed todescribe its construction in detail, explain its operation, and pointout in the appended claims its novel characteristics.

Referring to the accompanying drawings, forming a part of thisspecication, and in which similar characters of reference indicatecorresponding parts, Figure 1 is a sectional elevation of a water-tubeboiler, showing the improvements applied thereto; Fig. 2, a transversesection of Fig. l on the line :c x, shown on an enlarged scale; Fig. 3,a front elevation of the lower portion of the boilerfront on the samescale as Fig. 2; Figs. 4 and 5, detail views of the feeder; Fig. 6, adetail view of the sprocket-wheels and their shaft at the rear end ofthe chain grate; Fig. 7, a horizontal section on the line 'y y of Fig.l;

Fig. 8, a sectional elevation of the furnace and ash-pit with the chaingrate and feeder removed; and Fig. 9, a transverse section on the line ze', Fig. S.

A A are the inclined watentubes, and B the steam -drum, composing awell-known type of sectional boiler which I have chosen to illustrate inconnectionwith myinvention, it of course being understood that the saidinvention is applicable likewise to any other type of boiler than thespecial form shown.

C is the furnace, located beneath the front or elevated ends of thewater-tubes, and to which the draft is supplied from the point D throughthe sections of the graues.

E E are water-boxes at each side of the furnace-doors F, which form sidewalls for the doors and iuelose the receiving-space of the feeder abovethe doors.

To the water-boxes E, I connect the watertubes l l, which communicatewith the inud- `drum G or any suitable lower portion of the boiler, andare slightly inclined to promote circulation extending through thefurnace adjacent to the walls thereof and just above the grate-surfaceto form hre-backs for the fuel. The hand-holes 2, Fig. 3, afford accessto these tubes for cleaning them. To the Water-boxes E, I also connectthe uptake-pipes Il, which deliver the rip-current of water from thetubes l to the connecting-box I, intermediate to the headers and thesteam-drum of the boiler, or to any suitable upper portion of theboiler.

The pulverized coal or ashes at the sides of the furnace are banked upagainst the tubes l to seal the sides of the grate, and in order toeffectuate this purpose the tubes are made to converge from the front ofthe furnace toward the rear, as seen in Fig. 7, so that as the fuel ismoved rearward and becomes consumed and diminished in bulk it is crowdedtoward the center of the furnace to compensate for the reduction and tomaintain the depth at the. sides.

The ledges J .l of fire-brick overhanglthe tubes l in the furnace andprevent accumulation of ashes behind and around the said tubes, exposingonly the sides of the latter that are in direct contact with the movingfuel.

3 are sleeves that support the fire-brick ICO of the bridge-wall K atthose portions which the tubesl intersect, and the latter are therebyleft free to their movements of lineal expansion-without rupture to thewall.

L and M are overhanging radiating blocks composed of fire-brick, andthese being placed at an angle to the tire are adapted to absorb andradiate the heat, so as to intensify the temperature of the furnace.'lhe radiatingsurface L is by its inclined position adapted to receivethe heat from the body of the lire, assuming a glowing temperature, an dto transmit the same tothe fresh fuel beneath it with sufficientintensity to ignite the same at an earlier period than would be the caseshould the direct heat of the fire be employed to ignite the incomingfuel.

The chain grate N is composed of interlocking links having anywell-known or suitable form of construction, and it is operated oversprocket-wheels t 5 in the usual manner, the power being applied to theshaft t5 of the wheels 4. The chain grate travels oversupporting-rollers T, that extend at suitable intervals beneath thelinks between the side frames 8 8, that carry the sprockctwheel shaftsand form a carriage for the grate and its operating mechanism. 'lhecarriage S is provided with truck-wheels il, that fit a flanged track,upon which the grate may be rolled out bodily from the interior of thefurnace.

The upper edges of the side frames S S are inwardly flanged, as shown inFig. 2, to close the spaces that would otherwise be left at the sides ofthe grate-links, upon which the fire rests, and there are plates 10built int-o the side walls overhanging the flanges 11 of the frame 8adjacent to them and above which the tubes 1 are located. The plates 10being parallel with the flanges 11 effectually close the sides of thefurnace from the spaces exterior to the side frames 8, and I here remarkthat the inclined position of the plates 10 and of the flanges 11 permittheir surfaces to be brought closely together when the grate-truck ispushed back, affording a practicallyT tight joint throughout theadjacent surfaces.

The rear sprocket-wheel shaft 12, as more fully appears in Fig. G, isfurnished with a cylinder 13, enveloping it and extending between thesprocket-wheels, so as to fill the spaces as far as possible that wouldotherwise permit passage of cold air into the furnace at thereversing-point of the grate. The spaces exterior to the frames 8,adjacent to the side walls and opposite to the sprocket-wheels 5, arealso filled by flanged caps 18, that abut against the counter-surfaces20, Fig. 7, of the bridge-wall and have recesses 19, that inclose thehubs of the sprocket-wheels.

Below the grate-truck l employ one or more ash-pan trucks 14, (two beingshown,) that are withdrawn upon suitable trucks beneath and between thetracks of the grate. There is a partition-plate 15, that depends fromthe caps 18 of the grate-frame between the lower or returning links ofthe grate and the top of the ash-pan 1l, and there is also a partition1U beneath inthe ash-pan that corresponds in position with the plate 15when theash-truck is in place. A separation is thereby formed betweenthe body of the ash-pit and the chamber 17 to prevent passage of draft,and the ashes are precipitated into the chamber 17 as the graterevolves, the perfectly-consumed residue being received in a separatecompartment from that of the imperfectly-consumed coals that form aconsiderable percentage of the ash dropping at intermediate points fromthe fire.

l is the feeding-hopper that is provided at its neck with a feeding andcrushing device 21. The casing 22 of the feeder forms the crown of thefurnace-door casing, and the furnace-doors F swing on a fulcrum at 23,Figs. 1, 3, and 5. The doors are fixed to the shaft 21, having asuitable hand-lever at the side, by which the doors are raised, and theweight of the doors is eounterbalanced by a. weight 29, connected by achain to the lever 2S, the latter having a position relative to thedraft of the weight., whereby the doors are held in either their open orclosed position bythe gravity of the weight. Access is thereforeobtained to the fire independently of the feeding device and without thenecessity of removing any of the parts pertaining thereto, as llas beenthe case with the forms of mechanism used heretofore. The interior ofthe casing 22 is cylindrical, and the feeder 21 rotates therein in thedirection of the arrow, Fig. et. 'lhe feeder is composed of blades thatform pockets 25, which fill from the hopper by the gravitation of thecoal into them. Stich lumps of the coal as may be larger than theintended size are caught between the edges of the blades and theadjacent edges of the easing 22 and broken, and the portions aresuccessively discharged or showered upon the grate as the pockets comeopposite the opening 2G. It is to be observed that the neck of thehopper and the opening 26 are sufficiently apart with relation to theblades of the feeder to cut off ingress of air at all positions of thefeeder. The blades, moreover, are arranged spirally, as shown in Fig.et, whereby their rotation in the direction of the arrow will tend tospread the fuel toward the sides of the furnace, since thebulk wouldnaturally tend to pass through the center of the hopper. The spiral formis, however, made of sufficient pitch to more than equalize the saidtendency, inasmuch as it is desired to apportion the coal largely to theside of the furnace, for the purposes hereinbefore stated.

The rotation is imparted to the grate-shaft 6 and also to the feederlbymechanism substantially alike. The said mechanism consists in each caseof a worm-gear 30, having the teeth on the side of its periphery, a worm31 engaging therewith, a ratchetwheel 32 on the worm-shaft, and arock-arm 33, fulerumed on said shaft, bearing a pawl that en- IOO ITO

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gages with a greater or less number of teeth of the ratchet, accordingto thelength of stroke given to the rock-arm. The actuating-stroke isderived from any suitable source of given speed as the eccentrics 3e,and said stroke is varied by the adjustment of the eccentricrods atgreater or less-distance from the fulcruni of the lever 33. The relativeautomatic speeds of the feeder and the grate are thereby Varied,according to requirements of the fire.

What I claim as my invention, and desire to secure by Letters Patent,is-

1. The combination,with a chain Stoker, of a furnace the side wallswhereof converge in the direction of motion of the grate, whereby thefuel is concentrated during its passage and combustion.

2. The combination, with a boiler-furnace and a chain stoker, ofwater-circulatin g pipes extending longitudinally at the sides of thefurnace adjacent the surface of the grate to form portions of the sidewalls for retaining the fuel, said pipes connecting at their respectiveends with a lower portion of the boiler and with an upper portionthereof to promote circulation, substantially as described.

3. The combination, with achain Stoker, of water-circulating pipesextending longitudinally and adjacent to the furnace walls at or nearthesurface of the grate, said pipes converging toward the direction of thelineal movement of the grate, for the purposes specitied.

4. The combination, with a boiler-furnace and a chain stoker, of thewater-boxes E, form- .ing side walls of the fuel-receiving chamber,

water-circulating pipes extending longitudinally and adjacent thefurnace-walls and the surface of the grate and connected to a rear andlower portion of the boiler, and uptakepipes, as H, con necting with afront and upper portion of the boiler, adapted for the purposesspecified.

5. The combination of a furnace and a removable chain-grate frametherein, the adjacent surfaces whereof form joints inclined withreference to the direction in which the grate is inserted or withdrawnfrom the f urnace, for the purpose set forth.

6. In a chain grate, the combination of the side frames composing agrate-truck inclined at the upper edges toward the rear of the furnace,andsurfaces, as the plates l0, that incline correspondingly to the upperedges of the side frames and project from the furnace side walls to forma joint that is closed by the backward movement of the grate-truck, asdescribed.

7 The combination, with a chain stoker wherein a space is left at thereversing-point of the links adjacent the bridge-wall, of an ash-panadapted to receive the deposits from intermediate portions of the grate,and having a partitioned compartment beneath said reversing-point of thelinks to receive the ashes precipitated adjacent the bridge-wall.

S. The combination, with a chain stoker wherein a space is leftat thereversing-point of the links adjacent the bridge-wall, of apartition-plate located vertically beneath the reversing-point of thelinks, an ash-pan extending beneath the grate and beneath the saidspace, and a partition-plate within the ashpan adapted to form acontinuation of the first-named partition-plate when the grate and theash-pan are in place, substantially as and for the purposes specified.

t). The combination, in a chain stoker, with the sprocket-wheels andshaft at the reversing-point of the links, of cylinders enveloping thesaid shaft at the exposed spaces of the same between thesprocket-wheels, said cylinders having a diameter whereby they occupythe spaces intervening between the shaft and the inner surfaces of thelinks, adapted for the purposes specified.

NAT. XV. PRATT.

Witnesses;

H. F. PARKER, CHAs. HANIMNN.

